Communication devices, such as selective call receivers, are designed to respond to received digital information. Intersymbol interference is often introduced when the digital information is modulated for transmission. To recover the digital information, it is necessary to locate the center of a symbol of the demodulated signal in order to precisely determine the digital data corresponding to a level of the demodulated signal.
The conventional technique of synchronizing to the center of a symbol involves detecting edges of transitions of the demodulated signal. Symbol synchronization based on edge detection is adequate for most applications, though there is room for improvement. In particular, when the communication device operates in a simulcast system in which multiple transmitters transmit simultaneously in a coverage area, there is a significant degradation of the symbol synchronization accuracy using edge detection techniques.
Accordingly, a symbol synchronizer is needed for synchronizing to symbols in a demodulated signal in which the center of a symbol is determined by detecting "eye pattern" characteristics of the demodulated signal.